According to web inspector the problem is very likely that several resources are not loaded. The reason is that we are very likely too strict regarding some certificates (the same web page is perfectly rendered without any security warning in FF or Chrome). This is from the web inspector "Failed to load resource: Unacceptable TLS certificate: https://discourse.cdn.osmc.network/"
See: https://gitlab.gnome.org/GNOME/glib-networking/issues/96